The present invention relates to a heavy duty pneumatic radial tire, and more particularly it relates to a heavy duty pneumatic radial tire adapted to be used in the running on off road conditions.
A conventional heavy duty pneumatic radial tire for running on off road conditions has serious drawbacks that, when the tire rides on a projection formed on a road, separation of belt end portion occurs and separation of the turn-up end of the carcass ply occurs in the bead portion.
In order to prevent separation of belt end portion, the belt portion is wrapped with a rigid rubber and further with a flexible rubber, or a metal cord having a relatively large elongation is used in the belt to relax the stress at the belt end portion. However, the above described method is expensive due to the complicated arrangement of material members, but the resistance against the separation is not satisfactorily improved.
While, in order to prevent separation of turn-up end of carcass ply in the bead portion, the number of chafers having organic fiber cords, such as nylon cord and the like, is increased, or a rigid stiffener ruber is used to improve the durability of the bead portion. However, this method also is expensive due to the use of a large amount of material members, strain and stress are concentrated to the vicinity of the reinforced portion, and performance of the tire is decreased.
The present invention provides a carcass line, which has not the above described drawbacks and can advantageously prevent separation of belt end portion and separation of turn-up end of carcass ply in the bead portion.